Potential biomarkers for identification of mycobacterial cultures by proton transfer reaction mass spectrometry analysis.

RATIONALE: Several mycobacterial species can produce serious infections in humans, and the treatment required depends on the infecting species. Fast identification, ideally with minimal manipulation of the infecting species, is therefore critical; here, we propose a method potentially allowing cultures to be identified by headspace analysis and use it to screen for differences between mycobacterial species based on the volatiles released during growth. METHODS: Short-chain volatile organic compound emissions from two non-tuberculosis slow growing mycobacterial species, Mycobacterium avium and Mycobacterium kansasii, and a non-pathogenic fast growing species, Mycobacterium smegmatis, in Middlebrook M7H9 culturing media were followed online with a proton transfer reaction quadrupole mass spectrometer. RESULTS: Measurable differences between the headspace of the two slow growing mycobacteria M. kansasii and M. avium were found, as well as differences with respect to the faster growing mycobacteria M. smegmatis. Three compounds, attributed to sulfur-containing volatiles--dimethyl sulfide, propanethiol and dimethyl disulfide--were found to be specific to M. avium. CONCLUSIONS: Clear differences were detected in the low molecular weight volatile emissions compounds of the mycobacterial species under study, without the need for sample manipulation. Further studies with other mycobacterial species will reveal if the differences observed are specific to the species studied here. Furthermore, the use of an ion trap as a mass analyzer with the same ionization technique, allowing molecular detection over a wider molecular range, could allow the detection of additional biomarkers thus capturing a wider molecular range.

Proton Transfer Reaction Mass Spectrometry detects rapid changes in volatile metabolite emission by Mycobacterium smegmatis after the addition of specific antimicrobial agents.

The metabolic activity of plants, animals or microbes can be monitored by gas headspace analysis. This can be achieved using Proton Transfer Reaction Mass Spectrometry (PTR-MS), a highly sensitive detection method for trace gas analysis. PTR-MS is rapid and can detect metabolic responses on-line as they occur. Here, we study the headspace of actively growing cultures of paired ciprofloxacin sensitive and resistant bacterial strains (Mycobacterium smegmatis in Middlebrook M7H9 liquid media) after the addition of the antibiotics ciprofloxacin and gentamicin in real time. Following the emission patterns of the mycobacteria over time allowed volatile markers specific for the bacterial response to each antibiotic to be detected. A proportion of the measured responses were very rapid, occurring within three hours after the addition of the compounds and varied between isolates with different resistance phenotypes. Specifically, we observed a two fold increase of m73 (unidentified C4 compound) within 10h after the addition of ciprofloxacin and a threefold increase of m45 (acetaldehyde) within 4h after the addition of gentamicin as compared to values before the addition. Monitoring the emission of specific volatiles into the culture headspace thus has the potential for rapid drug susceptibility testing. Moreover, these and other differences in the measured responses to the two tested compounds provide evidence that monitoring multiple compounds may also give an indication of the mechanism of action of the compound added.

Hormone replacement therapy and acquired resistance to activated protein C: results of a randomized, double-blind, placebo-controlled trial.

Recent studies suggest that low-dose oral contraceptives may cause acquired resistance to activated protein C (APC). The aims of this study were to determine whether hormone replacement therapy (HRT) may also induce acquired APC resistance and to study the effects of APC resistance on the risk of recurrent thrombosis. The patients comprised 140 females with at least one previous venous thromboembolism (VTE), who were randomized to receive continuous treatment with 2 mg 17-beta-oestradiol and 1 mg norethisterone acetate (n = 71) or placebo (n = 69). Normalized APC sensitivity ratios (nAPCsr) were calculated by measurement of the effect of APC on thrombin generation in plasma collected at baseline and after 3 months of treatment. Of the 140 women, 121 had plasma samples collected both at baseline and after 3 months. The nAPCsr increased significantly (P < 0.001) on HRT (n = 62), both in females not carrying the factor V(Leiden) mutation [mean change 0.57 (95% CI 0.45-0.70), n = 50] and in females heterozygous for the factor V(Leiden) mutation [mean change 1.10 (0.71-1.49), n = 12], but remained unchanged on placebo (n = 59). The baseline nAPCsr as well as the increase in nAPCsr associated with HRT use was not higher in the five women who subsequently developed recurrent VTE. Free protein S and free TFPI were both important parameters for the acquired APC resistant phenotype. We conclude that HRT diminishes the efficacy by which APC downregulates in-vitro thrombin formation in a similar fashion to that observed with low-dose oral contraceptives, but the increase in nAPCsr alone is not sufficient to explain the increased risk of VTE associated with use of HRT.

Venous thrombotic risk in family members of unselected individuals with factor V Leiden.

The factor V Leiden mutation (FVL) leads to a seven-fold increased risk of venous thromboembolism (VTE). In thrombophilic families. 25% of carriers have experienced thrombosis before the age of 40 years. Aim of our study was to assess the association of FVL with VTE in first-degree family members of unselected symptomatic and asymptomatic carriers of FVL. We tested 197 relatives of consecutive thrombosis patients with FVL and 36 relatives of asymptomatic carriers on the presence of FVL and the occurrence of VTE. The incidence of VTE in relatives with FVL of symptomatic carriers was 0.34%/year. This was similar to the incidence in relatives with FVL of asymptomatic carriers. Kaplan Meier analysis in relatives of symptomatic propositi showed that at the age of 58 years, thrombosis-free survival was reduced to 75% in carriers and 93% in non-carriers (P <0.05). Carriers of FVL had a three times higher thrombotic risk than non-carriers. In combination with environmental risk factors, FVL clearly adds to the risk of VTE. The thrombotic incidence rate in these unselected relatives with FVL. however, is considerably lower than was seen in carriers of thrombophilic families (1.7%/year). Therefore, special care should be paid to individuals with a positive family history of venous thrombosis while exposed to these risk factors.

Preeclampsia and genetic risk factors for thrombosis: a case-control study.

OBJECTIVE: Recently, it has been proposed that hereditary coagulation abnormalities leading to an increased venous thrombosis risk may play a role in the development of preeclampsia. We tested this hypothesis in women who have had preeclampsia compared with matched control subjects. STUDY DESIGN: We conducted a case-control study of 163 women with preeclampsia during 1991-1996. Control subjects were matched for age and delivery date. Patients and control subjects were tested for the presence of factor V Leiden, prothrombin 20210A allele, protein C, protein S, and antithrombin deficiency. Logistic regression methods were used for data analysis. RESULTS: The prevalence of these genetic risk factors was similar in the patient group (12.9%) and the control group (12.9%; odds ratio, 1.0; 95% confidence interval, 0.5-3.9). Unexpectedly, we found a high prevalence of factor V Leiden in the control group (9.2%). CONCLUSION: We found no differences in the prevalence of genetic risk factors of thrombosis in women with preeclampsia compared with control subjects.

Careful selection of sample dilution and factor-V-deficient plasma makes the modified activated protein C resistance test highly specific for the factor V Leiden mutation.

The aim of this study was to evaluate critically the recently modified activated-partial-thromboplastin-time (APTT)-based activated protein C (APC)-resistance tests, which are more specific for the factor V Leiden mutation than the first generation APC-resistance tests. The only modification to these tests is the predilution of the plasma sample in factor-V-deficient plasma. The intended effect of this predilution is to bring the concentrations of all clotting factors, except factor V, to the same normal levels. This, in principle, makes the tests also suitable for assaying the plasma of patients treated with oral anticoagulants and heparin, or of patients with a lupus anticoagulant. However, not every factor-V-deficient plasma is suitable for this application. Because the factor V:factor VIII ratio is important in establishing the APC ratio, the factor-V-deficient plasma should contain a sufficiently high factor VIII concentration. We also found that the optimal dilution to obtain the same APC ratios for patients, whether or not treated with coumarins or heparin, is not the same for each test or factor-V-deficient plasma. We compared two modified APTT-based APC-resistance tests (one developed in our laboratory and one commercial) with respect to their ability to discriminate between carriers and non-carriers of the factor V Leiden mutation. Both modified tests gave complete separation of carriers and non-carriers of the factor V Leiden mutation whether or not they are treated with anticoagulants. This makes these tests very suitable for routine screening.

The factor V Leiden mutation (R506Q) is not a major risk factor for migrainous cerebral infarction.

The etiology of migrainous cerebral infarction is unknown, but may involve prothrombotic coagulation abnormalities. Therefore, we studied resistance to activated protein C and the presence of the Arg506Gln factor V Leiden mutation in 20 patients with migrainous cerebral infarction. Only one heterozygous carrier of the mutation was found, whereas other patients did not carry the mutation. This indicates that the factor V Leiden mutation is not a major risk factor for migrainous cerebral infarction.

Apparent different thrombotic tendency in patients with factor V Leiden and protein C deficiency due to selection of patients.

Both activated protein C (APC) resistance and protein C deficiency are associated with an increased risk for venous thrombosis. To assess their tendencies to venous thrombosis, we compared the median age of first venous thromboembolism in patients with factor V Leiden or protein C deficiency, who were identified either within unselected consecutive cases with a first deep venous thrombosis derived from a population-based case-control study, or identified by selection of patients with a deep venous thrombosis, who were referred for thrombophilIa work-up. The median age of onset for 92 unselected APC resistant cases was 43 years and for 13 unselected protein C-deficient cases 47 years. The median age at the first thrombotic event for 28 APC-resistant members of thrombophilia families was 29 years and for 50 protein C-deficient members of thrombophilia families 31.5 years. The median age of onset for all unselected patients (n = 105) was 45 years of age (range, 16 to 69 years) and the median age of onset for all selected patients from the thrombophilia families (n = 78) was 30.5 years (range, 16 to 67 years). These results show that within the case-control study and the family studies, the median age of onset is very similar in patients with APC resistance and patients with protein C deficiency. This suggests that APC resistance is not less severe with respect to risk of thrombosis than (heterozygous) protein C deficiency. In conclusion, the median age at which the first thrombosis occurs mainly depends on the way the patients are identified and not on the type of thrombophilia.

Activated protein C resistance: a comparison between two clotting assays and their relationship to the presence of the factor V Leiden mutation.

Resistance to the anticoagulant effect of activated protein C (APC resistance), a frequent abnormality in patients with a history of venous thrombosis, is known to be due, in the large majority of cases, to the presence of an abnormal factor V: the factor V Leiden. It is reasonable to surmise that screening for this abnormality should be performed with a clotting method for APC resistance, before submitting the patients with abnormal results to DNA analysis. The present study was performed on 216 individuals enrolled at the Bologna centre, of which 189 were unrelated patients with a history of juvenile venous thromboembolism and 27 were relatives with or without thrombosis. APC resistance was first measured in Bologna by a standard commercial method and then, in Leiden, by an in-house method: DNA analysis was performed in those cases in which at least one of the clotting methods was abnormal. The data obtained confirm the good performance and the optimal positive predictive value for the Leiden mutation (100%) of the Leiden in-house clotting method. Performance of the commercial method was less satisfactory but markedly improved by expressing the data in relation to the values simultaneously obtained with a normal plasma pool. Even with optimal data expression, however, the positive predictive value of the commercial method, versus DNA analysis, did not exceed 88%. It is concluded that further standardization of the commercial method here evaluated is necessary before it can be widely adopted for the screening of APC resistance and prediction of the presence of factor V Leiden.

Ischemic stroke in young patients with activated protein C resistance. A report of three cases belonging to three different kindreds.

BACKGROUND: A new pathological condition termed "activated protein C (APC) resistance" has recently been reported to be the most common hereditary blood coagulation disorder associated with familial thrombosis. APC resistance is characterized by a poor anticoagulant response to APC in the plasma of patients and is due to a defect of factor V. CASE DESCRIPTIONS: This report deals with three Italian families with inherited APC resistance in which stroke had occurred at a young age in one of the family members. One of the patients exhibited ischemic stroke at 8 months of age. Although deep vein thrombosis is considered the main clinical manifestation of the defect, its possible association with stroke is discussed. DNA analysis confirmed the presence of the 1691GA mutation in the factor V gene (factor V Leiden) in all patients with a normalized APC sensitivity ratio of less than 0.70. In three cases the APC sensitivity ratios were very low (approximately 1.2), with a normalized APC sensitivity ratio of approximately 0.4. DNA analysis confirmed that these patients were homozygous for the mutation. The clinical history of these patients suggests that homozygosity for the defect is compatible with life and does not seem to be associated with early or more severe thrombophilia compared with homozygous defects of other clotting inhibitors. CONCLUSIONS: The cases reported here suggest a possible association of inherited APC resistance with ischemic stroke in young patients. Case-control studies should be performed to assess the true association.

Preparation and structure of a water-in-oil cream containing lipid nanoparticles.

To obtain a topical dermatological product with a high degree of occlusivity combined with attractive cosmetic properties, a water-in-oil (w/o) cream containing small particles of solid paraffin was developed. Dynamic light scattering, freeze-fracture electron microscopy, polarization microscopy, and differential scanning calorimetry were used to characterize the cream. The preparation method essentially consisted of two steps. First, an aqueous dispersion of solid paraffin particles, with a mean diameter of 200 nm, was prepared with an oil-in-water (o/w) emulsifier. The aqueous dispersion proved to be extremely stable, and the particles had a spherical shape. Second, the aqueous dispersion was incorporated into the water phase of the cream during its production. After production of the cream, 68% of the paraffin was present as particles in the dispersed water phase. The size and shape of these particles did not change by the mechanical treatment during the production of the cream. At least 28% of the paraffin was present in the continuous oily phase, either as solid particles or in the form of a gel structure. At most, 4% of the paraffin was dissolved in this oily phase. The excess o/w emulsifier present in the aqueous phase of the w/o cream did not cause physical instability.

Laboratory diagnosis of APC-resistance: a critical evaluation of the test and the development of diagnostic criteria.

The APC-resistance test consists of two APTT's, one in the presence and one in the absence of a fixed amount of Activated Protein C (APC), and is a simple and reliable method to detect a reduced sensitivity to the anticoagulant action of APC (APC-resistance). At a fixed concentration of APC the prolongation of the APTT is dependent on the activator, the CaCl2 concentration, the citrate concentration in the sample, and on sample handling. The effect of sample handling can be reduced by calculating the APC-Sensitivity Ratio (APC-SR). The actual prolongation of the APTT is also influenced by low protein S levels (reduction of APC-SR) and by reduced levels of factors V, VIII and IX (increase of APC-SR). The APC-SR is most dramatically effected by reduced levels of factors II and X, which result often in "unmeasurable" APC-SR's in plasmas of patients on oral anticoagulant treatment. So at present no reliable APC-SR's can be measured in these patients. Patients treated with heparin can be tested after treatment of their plasma with Hepzym. The inter- and intra-assay variation in the APC-SR is 4% and 2%, respectively, when using the same batches of activator and APC. The variation which is introduced in the APC-SR by use of different batches of activator or APC, or by the use of different APC or CaCl2 concentrations, can effectively be avoided by expressing the result of the test in normalized-APC-SR (n-APC-SR).(ABSTRACT TRUNCATED AT 250 WORDS)

Mutation in blood coagulation factor V associated with resistance to activated protein C.

Activated protein C (APC) is a serine protease with potent anticoagulant properties, which is formed in blood on the endothelium from an inactive precursor. During normal haemostasis, APC limits clot formation by proteolytic inactivation of factors Va and VIIIa (ref. 2). To do this efficiently the enzyme needs a nonenzymatic cofactor, protein S (ref. 3). Recently it was found that the anticoagulant response to APC (APC resistance) was very weak in the plasma of 21% of unselected consecutive patients with thrombosis and about 50% of selected patients with a personal or family history of thrombosis; moreover, 5% of healthy individuals show APC resistance, which is associated with a sevenfold increase in the risk for deep vein thrombosis. Here we demonstrate that the phenotype of APC resistance is associated with heterozygosity or homozygosity for a single point mutation in the factor V gene (at nucleotide position 1,691, G-->A substitution) which predicts the synthesis of a factor V molecule (FV Q506, or FV Leiden) that is not properly inactivated by APC. The allelic frequency of the mutation in the Dutch population is approximately 2% and is at least tenfold higher than that of all other known genetic risk factors for thrombosis (protein C (ref. 8), protein S (ref. 9), antithrombin10 deficiency) together.

Venous thrombosis due to poor anticoagulant response to activated protein C: Leiden Thrombophilia Study.

We undertook a population-based case-control study to test the clinical importance of a hereditary abnormality in the coagulation system, characterised by poor anticoagulant response to activated protein C (APC), which is associated with familial thrombophilia. The abnormality was detected in 64 (21%) of 301 unselected consecutive patients younger than 70 years, with a first, objectively confirmed episode of deep-vein thrombosis and without underlying malignant disease. Among 301 healthy control subjects matched for age and sex, the frequency was 5% (14 subjects). Thus, there is a seven-fold increase in risk of deep-vein thrombosis in subjects with a poor response to APC (matched odds ratio 6.6 [95% CI 3.6-12.0]). In addition, there was a clear inverse relation between the degree of response to APC and thrombosis risk. In the families of the patients an autosomal dominant mode of transmission of the abnormality was confirmed. 9 of 10 thrombosis patients with a poor response to APC had 1 parent with a similar poor response, whereas 9 of 10 patients with normal tests had parents with equally normal tests. The abnormality was found in both parents of 1 patient with an extremely poor response to APC; this patient is probably homozygous for the abnormality. We conclude that the poor response to APC is the most important hereditary cause of venous thrombosis. Its high prevalence in a series of unselected patients will make testing of all thrombosis patients for this abnormality worth while.